Chapter 4 - Energy Analysis of Closed Systems - Problems - Page 207: 4-124

$T_1=54.5°C$

The total heat loss is: $Q=-6000 kJ/h \times 24h=-144 000 kJ$ The energy balance for this system is: $Q=\Delta U_{water}=mc_v(T_2-T_1)$ Given $m=1000\ kg, T_2=20°C, c_v=4.18\ kJ/kg$: solving for the initial temperature: $T_1=54.5°C$